The present invention relates to a desalting filtration device in which a filtration layer serving not only as a magnetic filter but also as a desalting column is disposed within a single vessel.
Steel structures such as various vessels and pipes used in the nuclear power plants, heat power plants, steam generating boiler plants and the like are gradually erroded by condensation and other fluids so that corrosion products (to be referred to as "cruds" in this specification hereinafter) such as particles of iron oxides (Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4 and so on ) are produced. As a result, the cruds gradually clog pipes and so-called salts resulting from neutralization reactions between acids and bases are resolved into fluids so that strong electrolytes are produced, thus corroding pipes or the like.
Electromagnetic filters may be used for removal of the cruds through filtration and desalting towers or columns may be used for desalting. So far these electromagnetic filters and desalting columns function independently and are arranged in parallel. Some of the reasons are as follows:
(1) A pressure vessel for accomodating an electromagnetic filter must be made of a non-magnetic steel around which water-cooled exciting coils and ferromagnetic yokes are mounted. On the other hand, a desalting column is made of a different material, i.e., a carbon steel so as to ensure mechanical strength thereof. Thus, combination of the pressure vessel for the electromagnetic filter with the desalting column would result in increase of the costs for welding and assembly.
(2) With a large-diameter pressure vessel for an electromagnetic filter, filter elements are flat and need a greater power for magnetization thereof. Thus, the diameter of the pressure vessel is limitative from the economical viewpoint and it is difficult to match the diameter of the pressure vessel with that of the desalting column.
Meanwhile, the same inventor devised the magnetic filter of the type as shown in FIG. 6 (Japanese Utility Model Application laid open under No. 53210/1983) for the purpose of improving the efficiency of removing the cruds and of reducing the installation area as much as possible. In this magnetic filter, inner tubes 41 partially and liquid-tightly extend through a vessel 1 having a liquid inlet 5 and a liquid outlet 6. The inner tubes 41 are closed at their upper ends as indicated by 42. Filter elements 9 in the form of ferromagnetic particles are in the space in the vessel 1 except the inner tubes 41 and permanent magnets 11 are vertically movable inserted into the respective inner tubes 41. The inner tubes 41 are made of non-magnetic material while the plugs 42 closing the upper ends of the inner tubes 41 are made of a ferromagnetic material. A guide 43 which is a lower portion of each inner tube 41 is made of a ferromagnetic material and is formed integral with the inner tube 41. The filter elements 9 are packed in the space which is defined around the tubes 41 by a pair of vertically spaced yoke-baffle plates 44, in such a way that the movements of the filter elements 9 are so restricted that they are not permitted to flow through the passage openings of the yoke-baffle plates 44. Upon energization of a magnet drive device 21, the permanent magnets 11 are displaced in the tubes 41 above the guides 43, so that the filter elements 9 are magnetized. Under these conditions, a liquid to be treated from a nuclear power plant is charged through the inlet 5 into the vessel 1 so that the cruds are attracted by the filter elements 9.
In order to remove the cruds attracted by the filter elements 9, the drive device 21 is activated so as to lower the permanent magnets 11 into the guides 43. After the filter elements 9 have been de-magnetized in that manner, cleaning water is charged through the outlet 6 into the vessel 1 so as to remove the cruds from the filter elements. The removed cruds are discharged together with the cleaning water through the inlet 5 out of the vessel 1.
The magnetic filter of the type described above with reference to FIG. 6 has not been designed to be stacked one upon another. As a consequence, when a desalting column is stacked, for instance, upon the magnetic filter, the overall height becomes too high.
Therefore, when a magnetic filter and a desalting column are used, they are installed at different locations or juxtaposed and are communicated with each other through pipes. As a result, the desalting-and-magnetic filter combination becomes large in size and consequently a large installation space is required.
The present invention was made to overcome the above and other problems encountered in the conventional magnetic fields and desalting columns.